The invention relates to a fuel injection jet of the type disclosed in German DE-OS 20 14 215. In this known fuel injection jet, a plurality of bores arranged in a common plane, emanate from a control ring channel, while bores in another plane emanate from a control pressure chamber. The jet needle which is lifted in accordance with the required output by the fuel pressure, forms a variable valve opening area with its control edge; and the control pressure chamber as well as the control ring channel with which the jet bores communicate are admitted with fuel.
The control pressure chamber and the control ring channel are intended to assure that the jet bores are fully exposed to the pressure of the fuel with the slightest release of the control edge of the jet needle. However, during operation of the combustion engine, the jet bores coupled with the control pressure chamber and control ring channel may be sucked empty due to the pressure fluctuations which occur during the operating cycle in the combustion chamber. Therefore, the additional sucked fuel from the volume of the control ring channel and the control pressure chamber into the combustion chamber of the combustion machine results in an undesirable increase in fuel consumption, and, in particular, to an increase of the polutants in the exhaust gas. Therefore, at each injection cycle, the jet needle must expose a large valve opening area instead of controlling the fuel quantity, so as to assure refilling of the control pressure chamber and the control ring channel, before injection occurs through the jet openings. Under these circumstances, control of the valve opening area by the jet needle cannot be assured due to the constant emptying and refilling of the control pressure chamber and the control ring channel which are connected with the jet bores. This is particularly pronounced at operation requiring low fuel dosages, such as during idling and in the lower load ranges. Since the jet bores are very large at the jet needle corresponding to the largest valve opening area, an insufficient atomization through the jet bores occurs, particularly in the idling position during low fuel supply, which results in insufficient fuel injection. Accordingly, there is a loss in the medium pressure, a high specific consumption, increased combustion rate and pure exhaust gas values.